The invention relates generally to vacuum toilet systems for aircraft, and, more particularly, to discharge valves with rotary gates in such systems.
Lavatories having vacuum toilet systems have been used in aircraft for many years. One such vacuum toilet system has a waste-receiving bowl connected to a waste reservoir by a sewer pipe. A discharge valve is mounted on the sewer pipe to selectively allow fluid communication from the bowl to the waste reservoir. To power the toilet system, the waste reservoir is maintained under a pressure that is substantially lower than the pressure in the waste-receiving bowl, which is typically under the near-atmospheric pressure of the aircraft's passenger cabin. Thus, when the discharge valve is opened, the pressure differential between the bowl and the reservoir causes the waste in the bowl to be drawn through the pipe into the waste reservoir.
A vacuum toilet system with a discharge valve is described in U.S. Pat. No. 4,713,847. This discharge valve has a cylindrical housing that has an inner chamber sized to contain a disk-shaped gate with a hole therein. One side of the housing has an inlet aligned with an outlet located on the other side of the housing. The waste-receiving bowl is connected to the inlet of the housing by one portion of a sewer pipe and the waste reservoir is connected to the outlet of the valve housing via another portion of the sewer pipe.
A drive mechanism selectively rotates the circular gate between an open position and a closed position. In the open position, the hole in the disk-shaped gate is aligned between the inlet and the outlet to allow fluid communication for the flushing of the toilet. In the closed position, the gate blocks fluid communication between the inlet and the outlet to prevent fluid flow from the pressure differential between the bowl and the reservoir.
Applicant's assignee, MAG Aerospace Industries, Inc. has for several years sold a discharge valve having a disc shaped gate valve, known as the Monogram Sanitation Orbital Valve, Part No. 14330-050. The experience which applicant's assignee has had with this valve shows that, while it generally functions acceptably, there can be a problem associated with a scale-like deposit that builds up on the sides of its rotating disk-shaped gate and over its internal housing parts over years of exposure to the minerals and chemicals in the toilet system fluid. The scale deposit reduces the distance between the sides of the disk and the sides of the inner chamber, thereby increasing the likelihood that the disk will eventually jam inside of the housing to render the valve inoperative. Because of this scale-like deposit problem, airlines must clean or replace the gate valve before other devices in the aircraft require major servicing. Accordingly, this maintenance problem undesirably reduces the time that an aircraft is available for revenue generating operation, resulting in lost income to the airline.
Another drawback associated with the gate valve described above is that its circular disk adds extra weight to the aircraft. While other gate valves for non-aerospace applications have used valves with non-circular gates, applicant is unaware of any such valve that has a partially circular or pie-slice shaped gate for the purpose of weight reduction in an aircraft vacuum toilet system. Accordingly, applicant is not aware of any prior art reference that teaches or suggests a weight reduction due to a relatively thin, pie-slice shaped gate valve for aerospace applications.
It should therefore be appreciated that there is a need for an aircraft toilet system with a light weight gate valve that resists jamming due to scale buildup, thereby reducing maintenance costs. The present invention fulfills this need.